Antiretroviral agents are the only therapy currently used for treating HIV dementia, but the treatment response is often poor. Selegiline is an approved and marketed selective monoamine oxidase type B inhibitor. However, at very low dosages in in vitro and in vivo systems, it blocks the formation of oxygen radicals and has a trophic effect on injured neurons through the stimulation of anti-apoptotic factors. A previous randomized double-blind, placebo-controlled trial of low dose oral selegiline suggested that selegiline treatment is associated with cognitive improvement in subjects with HIV-associated cognitive impairment. This study will evaluate the safety, tolerability, and efficacy of transdermal selegiline in patients with HIV-associated cognitive impairment. Transdermal selegiline has been well tolerated in healthy volunteers and in patients with Alzheimer's disease.